1. Field of the Invention
The present invention relates to an image input device for converting an image into an image signal and inputting the image signal into another device.
2. Description of the Related Art
FIG. 1 is a schematic view of the external appearance of a conventional image input device which is used in a video conference system or the like. As shown in FIG. 1, the image input device includes a base 1 on which to place an original 4 such as a map, a graph or a document, a post 2 disposed on the base 1, and a video camera 3 provided at an extending end of the post 2 and used to pick up an image of the original 4, so that a video image of the original 4 consisting of a text, a figure and others is sent out from the image input device.
When the original 4 is placed on the base 1, an image of the original 4 is picked up by the video camera 3 and is sent out from the image input device as a video output. The video output is converted into a standard format which is used in the video conference system, and the image of the original 4 is transmitted to a remote station which participates in a video conference.
In the conventional image input device, if the original 4 is obliquely placed on the base 1, the image of the original 4 is transmitted in the form of an obliquely picked-up image. As a result, conference participants in the remote station will be compelled to see the oblique image, and the video conference is hindered from smoothly proceeding.
FIG. 2 is a block diagram showing the arrangement of the video conference system.
The video conference system shown in FIG. 2 includes, as means for inputting an image, a video camera 301 for photographing a conference participant, an image input device (a so-called electronic OHP) 305 having a video camera 304 for picking up an image of an object or original 303 placed on a base 302, and a graphic input device (for example, a digitizer) 307 for inputting graphic data by means of an input pen 306 or the like. The video conference system also includes a television monitor 308 as means for outputting an image.
In the video conference system shown in FIG. 2, an image control device 309 controls the selective combination of images inputted by the video camera 301 and the image input device 305 and an image received via a communication control device 312 over an ISDN line which will be described later, as well as the outputting of an image to the television monitor 308.
The video conference system shown in FIG. 2 also includes a microphone 309 and a speaker 310, and the inputting of sound by the microphone 309 and the outputting of sound by the speaker 310 are controlled by a sound control circuit 311.
In the video conference system shown in FIG. 2, the communication control device 312 controls connection with a communication line, for example, the ISDN line, whereas a system control device 313 controls the entire system according to an operation of an operating device 314 and according to a graphic input by the graphic input device 307.
A plurality of terminals each of which is arranged in the above-described manner are interconnected via communication lines, so that a video conference can be conducted by communicating images and sounds therebetween.
In the above-described television conference system, operability and functionality are important.
However, in the case of the conventional image input device 305 used in the television conference system of FIG. 2 or the like, if an object is simply placed on the base 302, the object will be excessively large or small in size with respect to the photographic field of the video camera 304. If the zoom mechanism of the video camera 304 is not manually operated, an optimum video image will not be obtained.
Another problem is that if an original like a document is placed on the base 302 and is photographed, characters or lines on the original cannot be displayed with sufficient resolution without making the video camera 304 to zoom in to a sufficient extent.